Implantable prosthetic devices, particularly breast implants, are generally known. Most of these devices include a sack-like or envelope-like bladder which is manufactured from an elastomeric material such as silicone rubber and filled with a liquid or gel. The liquid or gel filling can be a silicone fluid or a saline solution. A combination of an elastomeric envelope and liquid or gel fill material is utilized to imitate properties of the tissue being replaced or supplemented.
Envelope-type or bladder-type implants may be pre-filled by the manufacturer or alternatively may be designed to be filled during or after surgery. As recognized by Purkait et al. (U.S. Pat. No. 5,019,101), it has been found to be desirable to utilize implantable devices which are not inflated prior to surgery. This allows the surgeon to determine a proper quantity of fill material or inflation depending upon the available space for tissue expansion or replacement. Further, in some situations, it is desirable to add fluid in stages subsequent to implant. In all applications wherein the device is purchased in a deflated state, it is necessary to include a fill valve assembly which allows addition of fluid or gel to the enclosure created by the bladder or envelope.
A recognized problem in the art when using a fill valve on an implantable prostheses is the potential leakage of the fill material through the valve assembly in the years subsequent to implant and filling. Prior art valves that have been used in such prosthesis, although providing a seal, may not provide an absolute seal, since some leakage can occur. It will be appreciated that although the leakage may be slight, and not noticeable over a short period of time, any decrease in fluid volume in the prosthesis over several years is unacceptable. Leakage has allegedly been tied to certain health problems, but also results in inability of the prosthesis to accomplish the cosmetic results for which it was implanted and filled.
The disclosure of Purkait et al. is directed to solving this recognized problem in the art. The Purkait et al. valve utilizes a main body portion having a channel for receiving a fill tube wherein the main body portion has an unevenly stressed section that includes a selected section of the channel. The unevenly stressed section is stressed so that the selected section of the channel folds back, occluding the channel, when the fill tube is withdrawn. The fill channel is formed by placing a Teflon sheet between two sheets of unvulcanized silicone rubber and heat-pressing the assembly. The Teflon sheet is then removed, leaving a channel between the silicone layers. As recognized by Purkait et al., the channel is not self-sealing, therefore, the sheets must be unevenly stressed to cause folding back in the channel area in order to prevent leakage.
It is believed that the use of a Teflon sheet which is removed from the channel prevents the channel from collapsing to a self-sealing position. That is, a gap will always occur at least at the edge or end of the channel where the Teflon sheet was placed in formation of the valve body. Uneven stressing of the valve body is required to overcome this problem. Further, the removal of a Teflon sheet and pre-stressing complicate the manufacture and assembly of a valve embodying the disclosure of Purkait et al.
Berjarano (U.S. Pat. No. 4,263,682) discloses the use of a release agent between sheets of unvulcanized silicone rubber which are heat-pressed. The only area that does not bond together is the portion that was pre-treated with the release agent. Thus, a channel is created between the sheets of silicone rubber. It is believed that a drawback of this method is that the release agent must be qualified for biocompatibility. Also, in manufacturing such device utilizing a release agent, there is difficulty in controlling the dimensions of the collapsible channel to assure adequate sealing, along with problems associated with gaps created by loss of the release agent, generally a powder. Any gap would reduce the self-sealing capability of the channel.
Accordingly, a need exists for an inflation valve assembly which is self-sealing and readily manufactured. Further, a need exists for a valve assembly which allows tight control of the dimensions of the insertion or fill channel. The insertion channel should be completely collapsible and self-sealing. The present invention addresses these needs as well as other problems associated with existing valve assemblies. The present invention also offers further advantages over the prior art and solves other problems associated therewith.